Abstract:Numerical simulations of ice cloud formation in the w=
ake of an aircraft flying at cruise altitude have been performed. The eng=
ine exhaust has been excluded from the simulations in order to study clou=
d formation due solely to aerodynamic effects. The ice is formed via homo=
geneous freezing nucleation of ambient haze droplets in the upwelling lim=
bs of the vortex pair behind the aircraft. Properties of wake ice clouds =
are compared with properties of contrails obtained with in situ measureme=
nts and recent simulations. In particular the authors find that aerodynam=
ically induced ice clouds are similar in microphysical and radiative resp=
ects to contrails that are formed from the nucleation of exhaust particle=
s. This means that under cold and moist conditions contrails as young as =
2-5 min may consist of similar amounts of aerodynamically produced and ex=
haust triggered ice crystals.